NEW YORK (Reuters) - Nearly half of American adults said the Republican healthcare reform measure is "not an improvement" over Obamacare, according to a Reuters/Ipsos opinion poll released on Friday.

The Republican bill, the American Health Care Act (AHCA), which is up for a vote in the House of Representatives later on Friday, is expected to cut the federal deficit while greatly increasing the number of Americans without health insurance.

Democratic leaders are unified against the bill while some conservative Republicans have criticized it for not doing enough to dismantle the Affordable Care Act, the measure familiarly known as Obamacare which was passed in 2010 and was the signature domestic achievement of former President Barack Obama.

According to the March 13-23 poll, 49 percent of American adults said the AHCA was "not an improvement" over Obamacare, which helped about 20 million people get insurance coverage. Another 33 percent said the Republican bill was "an improvement" over Obamacare, and the remaining 18 percent did not know.

The responses were largely split along party lines. Some 19 percent of Democrats and 53 percent of Republicans said the AHCA was better than Obamacare, while 73 percent of Democrats and 22 percent of Republicans said it was not an improvement.

The Reuters/Ipsos poll was conducted online in English in all 50 states. It first asked if people were familiar with the Republican reform. Those who said they were familiar were then asked whether they thought it was an improvement.

Altogether, some 1,741 people responded to both questions. This includes 673 Republicans and 829 Democrats. The poll has a credibility interval, a measure of accuracy, of 3 percentage points for the entire group and 4 percentage points for the responses from Democrats and the Republicans.